[Qemu-devel] [PATCH] scsi-generic: correct error management

[Qemu-devel] [PATCH] scsi-generic: correct error management

[Laurent Vivier]

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Hi,

this patch allows to fully use a tape device connected to qemu through
the scsi-generic interface.

Previous patch introduced tape SCSI commands management, this one
improve error case management:

- the SCSI controller command completion must be called with the status
value, not the sense value. In the case of scsi-generic, the SCSI status
is given by the field status of sg_io_hdr_t (the value is left shifted
by one regarding status codes defined in /usr/include/scsi/scsi.h)

- when a read is aborted due to a mark/EOF/EOD/EOM, the len reported to
controller can be 0. LSI controller emulation doesn't know how to manage
this. A workaround found is to call the completion routine with
SCSI_REASON_DONE just after calling it with SCSI_REASON_DATA with len=0.

This patch also manages correctly the block size of the tape device.

This patch has been tested with a real tape device "HP C5683A", linux
guest (debian etch) and tools like "mt", "tar" and "btape".

Windows guest is not better supported than before...

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Tested-by: Dietmar Maurer <dietmar@proxmox.com>
Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
---
 hw/scsi-generic.c |   94 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 76 insertions(+), 18 deletions(-)

Index: qemu/hw/scsi-generic.c
===================================================================
--- qemu.orig/hw/scsi-generic.c	2008-10-01 08:24:03.000000000 +0200
+++ qemu/hw/scsi-generic.c	2008-10-01 08:24:59.000000000 +0200
@@ -154,25 +154,26 @@ static void scsi_command_complete(void *
     SCSIRequest *r = (SCSIRequest *)opaque;
     SCSIDeviceState *s = r->dev;
     uint32_t tag;
-    int sense;
-
+    int status;
     s->driver_status = r->io_header.driver_status;
     if (ret != 0)
-        sense = HARDWARE_ERROR;
+        status = BUSY << 1;
     else {
         if (s->driver_status & SG_ERR_DRIVER_TIMEOUT) {
-            sense = HARDWARE_ERROR;
+            status = BUSY << 1;
             BADF("Driver Timeout\n");
-        } else if ((s->driver_status & SG_ERR_DRIVER_SENSE) == 0)
-            sense = NO_SENSE;
+        } else if (r->io_header.status)
+            status = r->io_header.status;
+        else if (s->driver_status & SG_ERR_DRIVER_SENSE)
+            status = CHECK_CONDITION << 1;
         else
-            sense = s->sensebuf[2];
+            status = GOOD << 1;
     }
-
-    DPRINTF("Command complete 0x%p tag=0x%x sense=%d\n", r, r->tag, sense);
+    DPRINTF("Command complete 0x%p tag=0x%x status=%d\n",
+            r, r->tag, status);
     tag = r->tag;
     scsi_remove_request(r);
-    s->completion(s->opaque, SCSI_REASON_DONE, tag, sense);
+    s->completion(s->opaque, SCSI_REASON_DONE, tag, status);
 }
 
 /* Cancel a pending data transfer.  */
@@ -251,6 +252,8 @@ static void scsi_read_complete(void * op
 
     r->len = -1;
     s->completion(s->opaque, SCSI_REASON_DATA, r->tag, len);
+    if (len == 0)
+        scsi_command_complete(r, 0);
 }
 
 /* Read more data from scsi device into buffer.  */
@@ -305,6 +308,12 @@ static void scsi_write_complete(void * o
         return;
     }
 
+    if (r->cmd[0] == MODE_SELECT && r->cmd[4] == 12 &&
+        r->dev->type == TYPE_TAPE) {
+        r->dev->blocksize = (r->buf[9] << 16) | (r->buf[10] << 8) | r->buf[11];
+        DPRINTF("block size %d\n", r->dev->blocksize);
+    }
+
     scsi_command_complete(r, ret);
 }
 
@@ -437,6 +446,9 @@ static int scsi_length(uint8_t *cmd, int
     case READ_12:
         *len *= blocksize;
         break;
+    case INQUIRY:
+        *len = cmd[4] | (cmd[3] << 8);
+        break;
     }
     return 0;
 }
@@ -619,6 +631,43 @@ static int get_blocksize(BlockDriverStat
     return (buf[4] << 24) | (buf[5] << 16) | (buf[6] << 8) | buf[7];
 }
 
+static int get_stream_blocksize(BlockDriverState *bdrv)
+{
+    uint8_t cmd[6];
+    uint8_t buf[12];
+    uint8_t sensebuf[8];
+    sg_io_hdr_t io_header;
+    int ret;
+
+    memset(cmd, 0, sizeof(cmd));
+    memset(buf, 0, sizeof(buf));
+    cmd[0] = MODE_SENSE;
+    cmd[4] = sizeof(buf);
+
+    memset(&io_header, 0, sizeof(io_header));
+    io_header.interface_id = 'S';
+    io_header.dxfer_direction = SG_DXFER_FROM_DEV;
+    io_header.dxfer_len = sizeof(buf);
+    io_header.dxferp = buf;
+    io_header.cmdp = cmd;
+    io_header.cmd_len = sizeof(cmd);
+    io_header.mx_sb_len = sizeof(sensebuf);
+    io_header.sbp = sensebuf;
+    io_header.timeout = 6000; /* XXX */
+
+    ret = bdrv_pwrite(bdrv, -1, &io_header, sizeof(io_header));
+    if (ret == -1)
+        return -1;
+
+    while ((ret = bdrv_pread(bdrv, -1, &io_header, sizeof(io_header))) == -1 &&
+           errno == EINTR);
+
+    if (ret == -1)
+        return -1;
+
+    return (buf[9] << 16) | (buf[10] << 8) | buf[11];
+}
+
 static void scsi_destroy(SCSIDevice *d)
 {
     SCSIRequest *r, *n;
@@ -673,17 +722,26 @@ SCSIDevice *scsi_generic_init(BlockDrive
     s->completion = completion;
     s->opaque = opaque;
     s->lun = scsiid.lun;
+    DPRINTF("LUN %d\n", s->lun);
     s->type = scsiid.scsi_type;
-    s->blocksize = get_blocksize(s->bdrv);
+    DPRINTF("device type %d\n", s->type);
+    if (s->type == TYPE_TAPE) {
+        s->blocksize = get_stream_blocksize(s->bdrv);
+        if (s->blocksize == -1)
+            s->blocksize = 0;
+    } else {
+        s->blocksize = get_blocksize(s->bdrv);
+        /* removable media returns 0 if not present */
+        if (s->blocksize <= 0) {
+            if (s->type == TYPE_ROM || s->type  == TYPE_WORM)
+                s->blocksize = 2048;
+            else
+                s->blocksize = 512;
+        }
+    }
+    DPRINTF("block size %d\n", s->blocksize);
     s->driver_status = 0;
     memset(s->sensebuf, 0, sizeof(s->sensebuf));
-    /* removable media returns 0 if not present */
-    if (s->blocksize <= 0) {
-        if (s->type == TYPE_ROM || s->type  == TYPE_WORM)
-            s->blocksize = 2048;
-        else
-            s->blocksize = 512;
-    }
 
     /* define function to manage device */